Liquid crystal display devices (LCD) are now in wide use as display devices for mobile phones, television sets, computers, etc. Conventional horizontal alignment type liquid crystal display devices which are prevalent today include TN (Twisted Nematic) mode and STN (Super Twisted Nematic) mode liquid crystal display devices in which a nematic liquid crystal material of positive dielectric constant anisotropy is used.
In recent years, with the view of improving the viewing angle characteristics and the display contrast, VAN (Vertical Aligned Nematic) mode vertical alignment type liquid crystal display devices have been developed and become increasingly prevalent.
FIG. 5 shows the structure of a pixel portion of a vertical alignment type liquid crystal display device described in Patent Document 1. This conventional liquid crystal display device is a transmission type liquid crystal display device which includes liquid crystal molecules 100 of negative dielectric constant anisotropy encapsulated between a TFT substrate and a counter substrate. The TFT substrate includes a substrate 110, a transparent electrode 111, an insulating layer 112 of silicon nitride or the like, a pixel electrode 114, a vertical alignment film 115, etc. The counter electrode includes a glass substrate 101, a common electrode 102 of ITO or the like, a vertical alignment film 103, etc. The transparent electrode 111 is connected to the pixel electrode 114 via a through hole 113 formed in the insulating layer 112. Provided around the pixel electrode 114 is a shield electrode 116.
When no voltage is applied between the common electrode 102 and the pixel electrode 114, the liquid crystal molecules 100 are aligned substantially vertically to the substrates because of the vertical alignment films 103 and 115. When a voltage is applied between the common electrode 102 and the pixel electrode 114, an electric field is produced which extends from the perimeter of the pixel electrode 114 toward a position right above the center of the pixel electrode 114. The liquid crystal molecules 100 are oriented along this electric field in such a manner that they lean toward the center of the pixel as shown in the drawing.
FIG. 6 shows an example of the shape of the pixel electrode 114. As shown in the drawing, the pixel electrode 114 has indentations recessed toward the inner area of the electrode. Three generally-quadrate parts of the pixel electrode 114 which are defined by the indentations are herein referred to as “subpixel electrodes 120”. Parts of the pixel electrode 114 which are defined by the indentations and which have a narrower width than the subpixel electrodes 120 are herein referred to as “bridge portions 121”.
Thus, the pixel electrode 114 has such a structure that the three subpixel electrodes 120 are connected together by the two bridge portions 121. The subpixel electrodes 120 and the bridge portions 121 are simultaneously formed of the same material in the same layer as an integral piece of pixel electrode.
Patent Document 2 describes a liquid crystal display device wherein each pixel includes a pixel electrode which has a slope surface configured for alignment control. The common electrode of this liquid crystal display device has slits at positions right above the pixel electrodes.
[Patent Document I] Japanese Laid-Open Patent Publication No. 2001-264784
[Patent Document 2] Japanese Laid-Open Patent Publication No. 2004-205902